A 33Mhz 32-bit bus has a data transfer rate of over 100MB/sec. So why can't a hard disk rated at 100MB/s attain 100MB/s in a PC? If ALL you're doing is copying files, shouldn't it be able to attain it's MAXIMUM data rate? Yes, it will - and you'll find it's not 100MB/s. Data bus limitations in PC account for SOME slowdowns, but not all - and they don't affect hard disk speed much. A hard disk in the XBox will attain a similar speed to the same speed in the PC, purely because any speed limitations are due to the physical construction of the drive.
You're forgetting that apart from the HDD, there's others hardware such as soundcard, internal modem, NIC etc, that also used the PCI bus. Those suckers also take bandwidth. And the figure of 40MB/s only apply to Intel i815 and i850 chipset ( or whatever chipsets that use the MTH ), as the northbridge and the southbridge aren't connected via PCI bus. All Athlon chipsets, and also Intel older chipsets such as BX and LX get much lower transfer rate than 40Mb/s, usually around 25 to 30MB/s at best. X-Box HDD is likely will connect directly to the faster system bus which is 200Mhz and should be able to clock higher speed than HDD in PCs. It's also why in the last minute, Intel were selected to provide CPU for X-Box, even that it's expensive compared to Athlon.
Incidentally, 4X AGP at 32-bit has a data bandwith of well over 400MB/sec. I don't think data bandwidth is a problem on the modern PC. The slowdown you see when data is transferred between oncard/main memory is because it's using the data bus AT ALL. ANY use of the data bus causes a slowdown, even if you're using DMA. Using it to contact a hard disk is even worse - ever heard of data seek time? So if the XBox swaps data to/from hard disk, that's a further reason to avoid it.
No, the slowdown happened because 1). The main memory IS slower than the video memory. 2). The AGP bus, even at 400MB/s as you've said, is slow. Wanna know why? AGP bus is just a derivative from the PCI bus. Hmm.. shared bandwidth again. And actually AGP 4x bandwidth is more than 1Ghz, theoritically. Compared with the X-Box bandwidth, AGP 4x still sucks. The 1Gb/s bandwidth is hardly used.
BTW - on the subject of textures - a 512x512 texture takes up 1MB of RAM, if you're using 32bit colour, and we all do. Given that a 512x512 texture could be standard for ANY enemy, modern games could well use 32MB of ram - multiple enemies on the screen, you, the backdrops, etc. On a GeForce/Radeon/whatever with 32MB of RAM you're laughing! On an XBox, you've just blown half your RAM on textures before any game data's been loaded. Sounds? Talking a few MB at least, and music's got to be taken into account. Remember, the 8MB DLS that came with FF8 was considered to be, well, "shit", so whether or not you're using synthesised music you want another 16MB for music. Oh dear, 3/4 of all RAM gone and we STILL haven't loaded anything other than textures or sounds. Basically, by the time the XBox comes out, 64MB of RAM is a REAL limitation. Even with texture compression (and, BTW, my graphics card supports S3TC in hardware, and it doesn't help that much) you still have REAL problems.
Here's is a link on how to calculate video memory taken by textures etc. [url="<a]http://www.planetquake.com/rocketland/haqsau/vidmemcalc.shtml[/url]" TARGET=_blank>PlanetQuake
512x512 textures is small, as Direct3D spec support up to 2048x2048. Calculate and with medium textures ( high textures don't make a difference on TV sets -especially the large ones ), pull all other at high selection ( 32bit, mipmap enabled, triple buffering etc. ) and still don't reach 20MB is video memory.
Music? One of the new feature in DirectX8 is that both DirectMusic and DirectSound are combined into one. So no more sucky sound like in FF VII. DLS is history now. You can create a loopable pre-recorded musics with Directx8, and also to take account with all TV sets around the world, 44Khz and 22Khz won't make a difference, also with mono and stereo, unless of course the TV set is also hooked to a home theathre sound system. Well, it's up to the developers to choose how the music should be played in their games.
About S3TC? Well what card did you use? Radeon or nVidia? FYI, nVidia have disabled S3TC support in all their drivers ( especially Det3 ), mostly to boost sales of their 64MB cards. Probably that's why you don't see any improvement in S3TC supporting games like Unreal Tournament and Soldier of Fortune. On other cards like Savage2000 which also support S3TC, the performance difference after enabling S3TC is noticeable, at least for me.
I'm not debating that the XBox will be a reasonable console; I'm saying that by the time it comes out, the standard PC will be pretty damn good, and within a year or two it'll far outclass the XBox
PC will of course overtake X-box in one year time or more after X-Box released. But to say a computer, even at that time, to be able to fully emulate X-Box is debatable. Texture handling, AC-3 support is just two cases which is interesting to see if any emulator programmers out there could handle.
Damn, if Aureal still lives now, maybe we already have a soundcard that can decode AC-3 in hardware, thus making X-Box ( and also PS2 ) emulation easier.
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